¥400,000 (Direct Cost : ¥400,000)

Using isolated rabbit chondrocytes, we investigated the effect of sex steroids produced by cartilarges on qrowth and maturation of bone. Both aromatase activity and 5-reductase activity existed in chondrocytes from ribs and articular cartilarges of 2-week-old Japanese white nibs. Chondrocytes from articular cartilarges had higher aromatase activity than those from rib cartilarges. In rib cartilarges, aromatase activity in growth plate was significantly higher than those in resting cartilarges. Preincubation of cultured chondrocytes with dexamethasone stimulated aromatase expression in all cell strains. The increment of dexamethasone-induced aromatase activity was significantly higher in chondrocytes from growth plate than in resting chondrocytes ( articular chondrocyte > rib growth chondrocyte > rib resting chondrocyte ), and was significantly higher in female chondrocyte than in male one. In contrast, 5-reductase activity was similar in each chondrocyte and in both sexes. Preincubation of chondrocytes with IGF-I did not induced activities of aromatase and 5-reductase.These results suggest that chondrocytes can produce estrogen and androgen, and estrogen production increases, and the maturation of cartilarge and bone may be advanced by paracrine action of those steroids, especially estrogen action.